With a recent demand for high integration of semiconductor devices, there have been proposed a stacked semiconductor device in which a stacked film is formed on a semiconductor substrate. The stacked film is obtained by alternately arranging interlayer insulation films and sacrificial films on top of each other. An example of the staked film is a silicon nitride film/silicon oxide film (SiN/SiO2).
A process of manufacturing the stacked semiconductor device includes, alternately forming the interlayer insulation films and the sacrificial films on the semiconductor substrate, and then selectively etching only the sacrificial films. As such, each of silicon oxide films used as the interlayer insulation films is required to have an increased etching resistance, e.g., a diluted hydrofluoric acid (DHF) resistance.
As a method for increasing the DHF resistance of the silicon oxide film, a method of forming a silicon oxide film (SiO2 film) by using, e.g., a triethoxysilane gas is proposed. This method increases the DHF resistance nearly twice as compared with a case where a dichlorosilane (DCS) gas is used to form a HTO (High Temperature Oxide) film.
However, the silicon oxide film formed using the triethoxysilane gas has a high carbon concentration, which causes a poor leak resistance. To address this, in some cases, an additional process is performed to reduce the carbon concentration in the silicon oxide film. However, such process may result in a degradation of the DHF resistance of the silicon oxide film. In this case, it is difficult to manufacture a stacked semiconductor device having good properties.